Question

When aniline is nitrated with nitrating mixture in ice cold condition, the major product obtained is:
A. P- nitroaniline
B. 2,4- dinitroaniline
C. O- nitroaniline
D. M- nitroaniline

Answer 1

Hint: To answer this question you must be familiar with properties and reactions of aniline. The amine group present in aniline has a lone pair on the nitrogen atom and is thus an electron donating and strong activating group.

Complete step-by-step answer:Nitration of aromatic compound is carried out using a mixture of concentrated nitric acid and concentrated sulphuric acid, known as the nitrating mixture at low temperatures.
We know that the amine group in aniline is an activating group and donates electrons to the aromatic ring from its lone pair through resonance. The lone pair is in conjugation with the pi bonds of the benzene ring and in the resonating structures, the electron density is maximum at the ortho and para positions thus making them more susceptible to electrophilic attack. Thus it is known as an ortho and para directing group.
Nitric acid is a strong oxidizing agent and on nitration aniline results into the formation of all three nitro anilines, i.e., O- nitroaniline, M- nitroaniline and P- nitroaniline. Para nitro aniline is the major product produced.

Thus, the correct answer is A.

Note: Meta nitro aniline is also prepared in significant amounts. This is because the amine group is protonated by the acid which results in the formation of anilinium ion which is an electron withdrawing and meta- directing group. This can be prevented by acetylating the amine group and protecting it from protonation. The products formed in this reaction are ortho and para products. Para nitroaniline is the major product formed in this reaction as well.